One of radiographic inspection apparatuses is a computed tomography (CT) apparatus. The CT apparatus comprises an X-ray tube for radiating X-ray fan beams, and a radiation detector comprising a large number of radiation-detecting elements. The X-ray tube and the radiation detector are arranged oppositely to each other with an object to be measured at a center. X-ray fan beams radiated from the X-ray tube pass through the object to be measured, and are detected by the radiation detector. With every radiation having a changed angle, X-ray absorption data of the object are collected to calculate X-ray absorbance at each position in each cross section of the object by computer analysis, thereby forming a cross-sectional image based on the X-ray absorbance. The radiation-detecting elements are constituted by scintillator cells and light-receiving elements. In the CT apparatus, the scintillator cells emit light when receiving irradiated X rays, and the light-receiving elements receive light from the cells to convert it to electric signals. Used as radiation detectors are detectors comprising scintillator cells and silicon photodiodes as light-receiving elements, or detectors comprising scintillator cells and photoelectron multipliers as light-receiving elements.
As a dual-array radiation detector comprising two types of scintillators having different compositions for different detection sensitivity distributions of radiation energy, for example, U.S. Pat. No. 4,511,799 discloses a dual-array radiation detector comprising first scintillators emitting light to be received by first diodes, and second scintillators emitting light to be received by second diodes. Also, WO 2006/114715 A discloses a dual-array radiation detector comprising a first light detector converting low-energy radiation to light which is then converted to electric signals, and a second light detector converting high-energy radiation to light which is then converted to electric signals. The detection sensitivity distribution of radiation energy is a distribution of radiation energy absorbed by scintillator plates, which depends on the composition of scintillators. However, U.S. Pat. No. 4,511,799 and WO 2006/114715 A do not disclose specific production methods of dual-array radiation detectors.
JP 2002-236182 A (U.S. Pat. No. 6,793,857) discloses a method for producing a one-dimensional or multi-dimensional detector array comprising scintillator cells having different widths in combination. In this method, (a) a composite layer comprising a radiation-sensitive sensor layer and a base layer is formed, and (b) the sensor layer is divided to individual insulated elements by cutting from the opposite side to the base layer, thereby forming partition walls in the sensor layer. However, in the method of JP 2002-236182 A, the number of steps increases with larger numbers of cells, making efficient production difficult.
JP 2001-174564 A discloses a dual-array X-ray detector comprising pluralities of scintillator elements reacting X rays of different energy levels, which are arranged in an X rays passing direction, and light-detecting elements each corresponding to each scintillator element, which are arranged in a perpendicular direction to the scintillator elements, pluralities of scintillator elements and pluralities of light-detecting elements being respectively arranged in line. Pluralities of scintillator elements are integrally molded with a light-reflecting material. However, JP 2001-174564 A does not specifically disclose a method for producing the dual-array X-ray detector.
JP 2009-524015 A discloses a method for producing a scintillation array comprising the steps of forming a scintillation ceramic wafer, forming pluralities of slits in two perpendicular directions on an upper surface of the ceramic wafer, and partially oxidizing a surface of the ceramic wafer to form a reflective layer. However, the method of JP 2009-524015 A forms a scintillation array by one type of a scintillation ceramic, not by two types of scintillation cells.